Rolling mill

ABSTRACT

The present disclosure relates to an apparatus for allowing the rolls of a rolling mill to be quickly removed from and replaced into the mill stand. It provides a pair of bars for interconnecting the opposite bearing chocks of one of the rolls, all four elements of which are provided with wheels. The wheels are supported by two pivotal rails that extend between the housings of the mill. The rails during operation of the mill are positioned away from the bars, but, when the rolls are to be changed, they are positioned under the bars. The rolls are received in front of the mill by a side shifter having three discrete and spaced-apart support areas that support two rollcarrying platforms. Because of the spacing of the areas, the platforms have movable liners that span the spaces. A central area is movable axially of the mill for removing both the work rolls and the backup rolls from a position in front of the mill to a position remote relative thereto.

1Jnited States Patent 1 1 11 3,738,142 Adair 1451 June 12, 1973 ROLLING MILL 57] ABSTRACT Inventofi James Richard Adair, Pittsburgh, The present disclosure relates to an apparatus for al- [73] Assigneez United Engineering and Foundry lowing the rolls of a rolling mill to be quickly removed 7 Company Pittsburgh, from and replaced into the mill stand. It provides a pair of bars for interconnecting the opposite bearing chocks Flledi y 1971 of one of the rolls, all four elements of which are pro [21] Appll NOJ 146 228 vided with wheels. The wheels are supported by two pivotal rails that extend between the housings of the mill. The rails during operation of the mill are posi- U-S. tioned away from the bars but when [he rons are to be [51] Int. Cl B2lb 31/08 changed, they are positioned under the bars. The roll Fleld of Search are received in front of the a ide hifter having three discrete and spaced-apart support areas that sup- References Clted port two roll-carrying platforms. Because of the spac- UNITED STATES PATENTS ing of the areas, the platforms have movable liners that 3,436,945 4/1969 Karnkowski 72 239 span the p A Central area is movable axially Ofthe 3 633 4 2 1972 p k et 72 239 X mill for removing both the work rolls and the backup 3,491,570 1/1970 Beard 72/239 rolls from a position in front of the mill to a position re- 3,540,253 11/1970 Kollek et al. 72/239 mote relative thereto. 3,540,254 ll/l970 Bode, Jr 72/239 3,566,498 3/1971 Kato et al. 72/239 Primary ExaminerMilton S. Mehr 9 Claims, 8 Drawing Figures Attorney-Henry C. Westin 1s F49 l= 48 52 5 53 11141 1* 7 E A. 1 1 IV E 50 a 5 l8 47 1 11111.1, AREA PATENIEB Jul 1 3 Mill-HQ m.. &L 0 I qwc 101m 4401 (mud 44.!

ENV ENTOR JAMES R. A'DAIR HENRY c. wEs'rqN ATTOR NE Y PAIENTED Y 2 W5 .v u a .7 W W iil H H- ung I II V fi -mummr uu n I u a um m mm a. llllllll .u 3 6 Y INVENTOR JAMES R. ADAIR HENRY C. WESTIN ATTORNEY mmzuwzm mum I) on INVIENTOR JAMES R. ADAIR.

HENRY c. WESTIN ATTORNEY FIG. 7

ROLLING MILL In recent years many attempts have been made in the rolling mill industry to provide an economical and quick procedure for removing and replacing the rolls of the mill. While much attention has been given to work roll changing, since they usually require replacement much more often than the backup rolls, backup roll changing has also received attention. One of the disadvantages of many of these prior attempts has been in the expense, cumbersomeness, and ineffective manner in which the rolls were supported during roll changing, both while in the mill and when removed therefrom onto a turntable or side shifter or similardevice.

It is the object of the present invention to provide for the improved roll changing of the rolls of a mill or like device, such as a rubber or paper calender.

More particularly, it is the object of the present invention to provide a simple and economical construction for supporting the roll or rolls during a roll changing operation, both in their movement in the mill and when outside the mill.

A still further object of the invention is to provide roll-supporting rail means including means for moving the rail means from an inoperative position out of alignment with the windows of the mill to an operative position in alignment with the windows where they support both the wheels of a bar that interconnects the opposite bearing chock assemblies of one of the rolls and wheels of the opposite bearing chock assemblies of the one roll.

Another object of the present invention is to provide a side shifting assembly for receiving an old set of rolls from the mill and for replacing them with a new set of rolls, in combination with means extending between and connected to the opposite bearing chockassemblies of one of the rolls of the mill, support means extending between said housing having a surface for supporting said connecting means, and means for engaging one of said roll assemblies for removing said roll assembly from said mill. I

These objects, as well as other novel features and advantages of the present invention, will be better appreciated when the following description is read along with the accompanying drawings, of which:

FIG. 1a is an elevational side view of a rolling mill incorporating the features of the present invention showing in full line a set of work rolls about to be removed from the mill by a first tractor and a second tractor employed for removing the backup rolls in position to accomplish this operation after the work rolls have been removed and side shifted, and in phantom line, a replacement set of work rolls ready to be inserted into the mill,

FIG. 1b is a continuation of FIG. 1i: illustrating the backup roll shown in FIG. 1a retracted fromthe mill to the roll shop area and illustrating the center support of the side shifter illustrated in FIG. la in its retracted position in readiness to receive a new roll set of work rolls or the stool for the backup rolls,

FIG. 2 is a view similar to FIG. la with certain parts broken away for clarity,

FIG. 3 is a section view taken on lines 3-3 of FIG.

FIG. 4 is a section view taken on lines 4-4 of FIG.

FIG. 5 is an end view of the side shifter illustrated in FIG. 1a showing in phantom old and new work roll sets, and in full line the stool for the backup rolls,

FIG. 6 is a plane view of the side shifter shown in FIG. 5 without the stool, and

FIG. 7 is an enlarged sectional view of a portion of FIG. 5, but showing the side shifter moved sideways.

With reference first to FIGS. 1a, 2, 3 and 4, there is illustrated a rolling mill stand comprising a pair of spaced-apart upright housings 11 and 12, the housings having customary windows for receiving work roll assemblies 13 and 14, each of which will be supported and backed up by a backup roll assembly, only the lower backup roll assembly 15 being shown in the drawing. The housings, in accordance with general practice are supported on parallel bed plates 18 and 19 that extend in a direction parallel to the axes of the rolls.

The upper work roll 13 is rotatably supported in bearing chock assemblies 21 mounted on the journals on its opposite ends and which, as shown in FIG. 4, assume a generally rectangular shape. The bearing chock assemblies provided for the lower work roll 14 are somewhat differently constructed and, as best shown in FIG. 2, consist of generally square-shaped bearing chock assemblies 22, which, as shown in FIG. 4 at their lower portions, have wing portions 26 which extend outward from the main vertical portion of the chock assemblies and which portions receive wheels 27 that are positioned so as to rotate about horizontal axes. At this point it may be well to refer to the construction of the housing, asillustrated in FIG. 4 with respect to the work roll assemblies 21 and 22, in which it will be noted that the housings 11 and 12 have inward projecting portions 28 for receiving the adjacent surfaces of the bearing chock assemblies 22 of the lower work roll In again referring to FIG. 2, it will be noted that the bearing chock assemblies 22 of the lower work roll 14 are interconnected by a pair of parallel extending bars 30, which are shown with greater clarity in FIG. 3 in connection with the operator side bearing chock assembly. To the lower surface of the bars 30 there are provided at each end two sets of wheels 31 arranged adjacent their opposite ends, each set consisting of three wheels each; whereas, the wheels 27 associated with the lower work roll chock assemblies 22 are made up into two sets for each assembly in which each set comprises two wheels.

In the center of the mill, as one views FIG. 2, there are provided two generally upright rails assemblies 32 and 33 which extend between the opposed housings 1 1 and 12 on either side of the plane containing the work rolls and backup rolls, and which have a length approximating that of the face of the work rolls. The'rail assemblies 32 and 33 include horizontally disposed rails 34 arranged at the upper inward ends, and, at their lower ends, they are provided with trunnion shafts 35 arranged in a direction parallel to the axes of the rolls which allow the rail assemblies 32 and 33 to be pivoted in a direction towards and away from the vertical center line of the mill, as one views FIG. 4. Actually, FIG. 4 shows in phantom the retracted position of the rail assemblies 32 and 33 and in full line the extended or operating position in which the rails 34 are positioned directly under the wheels 31 of the interconnecting bars 30. The rail assemblies 32 and 33 are moved between these two positions by individual piston cylinder assemblies 38. Before leaving FIG. 4, it will be noted that the upper work roll chock 21 is shown supported by the lower work roll chock 22. This support is accomplished by a pair of stools 39, it being appreciated that a similar pair of stools will be provided for the operating side bearing chock assemblies of the work rolls 13 and 14.

With reference to FIG. 3, it will be noted that the bearing chock assembly 22 of the lower work roll 14 and particularly the wheels 27 thereof are unsupported until the roll assembly 14 is moved axially towards the operating side of the mill, at which time the wheels 27 will engage a pair of tracks 41 that serve as extensions of the rails 34, the tracks 41 actually being part of a side shifter assembly to be described later. At this point it is only necessary to point out the significance of the spacing between the wheels 27 of the lower work roll bearing chock assembly 22 and the wheels 31 of the bar assemblies 30. The spacings between the sets of wheels 31 and 27 with respect to the bearing chock assemblies 22 are such that the wheels 31 will support the roll assemblies until the wheels 27 come in contact with the tracks 41 as the roll assembly moves from left to right in FIG. 3 with respect to the operating side chock 22 and that the reverse takes place with respect to the drive side chock 22 again as the roll assembly is moving out of the mill from left to right, as one views FIG. 3. In returning the roll assemblies to the mill, the reverse engagement will take place; that is to say, with respect to the drive side chock 22, the wheels 31 most adjacent to the drive side chock 22 will retain engagement and support with the tracks 41 until the wheels 27 of the chock 22 engage the rails 34. Thus, the space between the mill housing 12 and the side shifter is bridged.

Turning now to the side shifter, reference will be made to FIGS. 1a, lb, 2, 5, 6 and 7 which comprise a pair of horizontal supporting beams 43 that serve to support a superstructure consisting of vertical columns 44 which at the top support a horizontal substructure 45 arranged approximately at the mill floor line, only one of which beams is shown in the drawings extending in a direction away from the mill on the operators side and parallel to the plane containing the axes of the roll. This entire assembly is retractable from a position in front of the mill to a position remote therefrom into the adjacent bay that constitutes the roll shop by virtue of being slidable over the beams 43 as advanced by a tractor 46. The tractor consists, in part, of a motor 47 which drives a gear, not shown, about a vertical axis, which, in turn, meshes with racks mounted on the beam 43 to constitute a rack and pinion design and through which means the tractor 46 is advanced to and from the mill.

It might be mentioned here, as the legend indicates in FIG. 1b, that the assemblies are actually shown in FIG. 1b in the roll shop area, whereas, in FIG. 1a, the assemblies are shown in the mill area. As probably best shown in FIG. 1b, the side shifter takes the form of a top platform 48 which supports a second tractor 49 made of a generally similar construction as the tractor 46 and consists of a motor 51 including a gear unit having a gear rotatable by a vertical axis, not shown, which engages a pair of racks mounted on the platform 48 which allows the tractor to be advanced toward and away from the mill. It will be noted that the tractor as illustrated consists of a pair of hooks 52 mounted approximately in line with the lower work roll chock 22 to which the hooks will engage, as will be more fully explained hereinafter.

Towards the front of the platform 45 the side shifter takes the form of an independent platform 53 which is best shown in FIGS. 5, 6 and 7. The platform 53 is made up in the form of a box having at its two outer ends two uprights 54 to which there is mounted on the lower portions liners arranged in a direction so that the platform 53 may move to the left or right as one views FIGS. 5 and 6. This movement with respect to the side shifter is guided by projections formed on the end portions, not shown, of the liners 70, the liners 70 sliding over a liner 55 secured to the subplatform 45. Still referring to FIGS. 5 and 7, it will be noted that the upright members 54 of the platform 53 are provided at their upper surfaces with rails 58 which serve to support the wheels 27 and 32 of the work roll assembly 14. As shown in FIG. 1a, the tractor 49 is adapted to be advanced from the far side of the subplatform 45 to a position where it may be brought adjacent to the operating side of the mill and where its pair of hooks 52 can be caused to engage a pair of cooperative hooks provided on the lower work roll chock 22 and which, in FIG. 3, has been identified by the reference character 61.

Intermediate the mill area and roll shop area, and located in the latter, between which the platform 53 must pass when retracted from the mill is the other part of the side shifting assembly, which is best illustrated in FIGS. 5 and 6. As shown on either side of the center line containing the rolls, and, more particularly, the platform 53, there are arranged two support areas 62 and 63. These support areas at their top have a similar guiding construction to that provided with respect to the platform 53 and consist of liners 64 that support the upright members 54 of the platform 53 or a similar platform 65, which is illustrated in FIGS. 5 and 6 at the right as one views this figure. It will be appreciated that there are provided in fact only two platforms similar to 53 and 65 and that they shift from left to right and right to left, as one views FIGS. 5 and 6, so that at any given time these platforms are either supported by one or the other of the support areas 62 and 63 and the subplatform 45.

The platforms 53 and 65 are adapted to be selectively interconnected by quickly insertable pairs of links 66, the platform 65 being connected by a similar pair of links 67 to a guide 68 which, in turn, is connected to a piston cylinder assembly 69 which furnishes the traverse movement for the platforms 53 and 65. As FIG. 5 illustrates, there is a space or a gap between the sup port areas 62 and 63 on either side of the platform 53. In order to bridge this gap, the platforms 53 and 65 are provided with the liners 70 arranged at the ends of the platforms and come into contact with the liners 64 of the support areas 62 and 63, by which means the platforms 53 and 65 are supported. The length of the liners 70 are such that the liners will come into engagement with the subplatform 45 or either the supports 62 and 63, depending on which direction the platforms 53 and 65 are moving.

It is a feature of the present invention to provide for the employment of the side shifter assembly or at least a part thereof for changing the backup rolls of the mill, in which connection the tractor 46 will be employed and its hook 71 brought into engagement with a beam 72 by which the lower backup roll is supported. According to the usual custom, this beam 72 is always mounted in the mill when the backup roll is in the mill and is adapted to be removed with the rolls during the roll changing of the backup rolls.

In now referring to FIG. 5, there is shown with respect to the platform 65 a backup roll changing stool 73 which is adapted to be supported by the platform 65. Before the stool can be so positioned it is first placed on the platform 65 in the roll shop and then, by the tractor 46, is brought to the side shifting area for side shifting to the support area 63, where it is shown in FIG. 5, to await the removal of the old work roll set. The transfer to the area 63 is accomplished by inserting the links 66 to interconnect the two platforms 53 and 65. The old roll set is positioned on the platform 53 in a manner yet to be explained as shown in FIG. 5 and with the links still connected to the platforms 53 and 65. By operation of the cylinder 69, the platforms are shifted to the left which places the old roll set in the support area 62 and the stool 73 on the subplatform 45. At this point, the links 66 are uncoupled. Once supported by the subplatform 45, the stool 73 can be brought to the mill, first by operating the tractor 46 which will move the substructure 45 and, hence, the platform 65, and then by operation of the tractor 49 to position the platform 65 adjacent to and directly in front of the mill. Once the stool is within the mill, it will come into a position between the bearing chock assemblies of the backup chocks and allow the upper backup chocks to be brought into a supporting relation with the stool. After this occurs, the tractor 46 will engage the beam 72 and remove both backup roll assemblies to the roll shop, which position is shown in FIG. lb.

In changing the work rolls, in which case the backup rolls with the beam 72 will remain in the mill, for the purpose of discussion let it be assumed that the platform 53 is in the center and that the platform 65 is at the right as viewed in FIGS. 5 and 6. In this position, the platform 65 will receive a pair of new work roll assemblies, the exact complement of the assemblies to be removed from the mill and which will be supported by stools similar to the stools 39. The new pair of roll assemblies will have been brought to this position by placing them on the platform 65 in the roll shop area and then transferring them for side shifting to the support area 63. Prior to the actual side shifting of the new roll set to the support area 63, the platform 53 will remain supported by the support area 62 and be interconnected to the platform 65 by the links 66 once the platform 65 has been brought to the side shifting area. In this connection, it should be noted that the transfer of the subplatform 45 from the roll shop area to the side shifting area and then to the mill area is effected by the advancement of the tractor 46 which, as previously noted, advances the subplatform 45, which may be supporting one or the other of the platforms 53 or 65. With the new work roll set so positioned and the platform 53 supported by the subplatform 45and the links 66 uncoupled, the tractor 49 will be advanced to the position shown in FIG. la, where the tractor 49 engages the work roll hooks 61 of the lower work roll chock 22. When this is accomplished, the tractor 49 will then be retracted to a position where it will be brought entirely on the platform 53, as shown in phantom in FIG. la. The tractor 46 will again be operated to bring the side shifter assembly into a position where the platform 53 is centrally disposed with respect to the platform 65 or into the position shown in FIGS. 5 and 6 to allow a side shifting to occur on operation of the piston cylinder assembly 69. Before this can take place, the link 66 must be inserted to interconnect the platforms 53 and 65 after which the cylinder 69 can be operated to shift the old or worn roll set to the left where the platform 53 will be supported by the support area 62 and the platform 65 will assume a supporting position on the subplatform 45. Once the new roll set has been positioned in front of the mill, the tractor 46 will again be operated to advance the subplatform 45 to the position illustrated in FIGS. 1a and 2 from which the tractor 49 will be operated to move the new rolls from the phantomline position shown in FIG. la into the full-line position and within the mill. Once the hooks 52 of the tractor 49 have been removed from the lower work roll assembly 22, the subplatform 45 may be retracted again to where the worn or old roll set can be transferred from the support area 62 back to the platform 45, after which the old roll set can be transferred to the roll shop area.

In accordance with the provisions of the patent statutes, I have explained the principle and operation of my invention and have illustrated and described what I consider to represent the best embodiment thereof.

I Claim:

1. In a rolling mill having drive side and operating side housings for receiving a pair of work roll assemblies,

a window in each of said housings,

said work roll assemblies including bearing chock assemblies mounted on their opposite ends and received in said windows, means extending between and connected to the opposite bearing chock assemblies of one of said roll assemblies and including two separate bars arranged on opposite sides of said one roll assembly,

support means extending between said housings including two separate support members, ecah having surfaces for supporting a different one of said bars and each having an operative and an inoperative position, means for bringing said support members from their inoperative positions remote from said bars into their operative positions where they assume a supporting relationship with a different one of said bars, and

means for engaging one of said roll assemblies for removing said roll assemblies from said mill during which the roll assemblies are supported by said support means.

2. In a rolling mill according to claim 1 wherein said bars extend between said housing and outside of said' windows, each including roll supporting wheels arranged adjacent each of the opposite ends thereof,

roll supporting wheels mounted on said bearing chock assemblies of said one roll in a manner that the adjacent wheels of said bars and bearing chock assemblies form cooperating sets,

a work roll assembly platform arranged at the operator side of said mill having one of its ends adjacent the outside of said window of said operating housing and adapted to receive and support the wheels of said bearing chock assemblies and bars, and wherein the relative space between the wheels of each cooperating set is such that the respective ends of the roll assemblies are supported at all times by at least one of the wheels of each set as the roll assemblies are removed from the mill and pass through said spaces.

3. In a rolling mill according to claim 2 in which the axes of said work roll assemblies are arranged in substantially the same vertical plane, and wherein there is means for causing said bearing chock assemblies of the lower work roll assembly to assume a supporting relationship with the bearing chock assemblies of the upper work roll assembly.

4. In an apparatus for supporting a roll assembly of a rolling mill while the roll assemblies are being removed from and replaced into the mill comprising:

said mill including a housing having a window therein that receives said roll assemblies,

a side shifting assembly arranged in front of said window,

said side shifting assembly comprising three discrete and spaced-apart roll supporting members, one arranged in front of said window in a plane containing the axes of said roll assemblies when mounted in said mill and the other two arranged parallel to and on either side of said first'roll supporting memher,

two movable support means adapted to be selectively supported at any one time by two of said three members,

means extending between and interconnecting said support means for causing said support means to move as a unit to and from a position in front of said window,

means for effecting said movement of said support means,

said support means including means movable with said support means and arranged to bridge said spaces between said members to provide a support for said support means when moving through said spaces, and means for moving a roll assembly to and from said window onto one of said support means positioned in front of said window.

5. In an apparatus according to claim 4 wherein said support means each includes a pair of tracks for supporting a pair of surfaces provided on one of said roll assemblies,

rails arranged in said mill alignable with the tracks of said support means when the support means are shifted to a position in front of said window,

said means for bridging said spaces comprising liners arranged at the opposite sides of each support means and adjacent said slides having a length greater than said spaces between said member.

6. In an apparatus according to claim 4 in which said means for effecting movement of said support means includes a power means connected to one of the outside support means.

7. In an apparatus according to claim 4 including means for stationarily supporting the two outside supporting members,

means for movably supporting the central supporting member, and

means for effecting said movement of said central supporting member. 8. In an apparatus according to claim 7 wherein said roll assemblies comprise work roll assemblies and wherein said mill includes a backup roll assembly for each work roll assembly,

means in front of said window for supporting said backup roll assemblies when removed from said mill, and

said central supporting members including means for engaging one of said backup rolls to effect said removal.

9. An apparatus according to claim 8 including a stool supportable by one of said support means for transferring to said mill after the work roll assemblies thereof have been removed,

means on said stool for allowing it to be supported by a lower of said backup assembly when in said mill, and

' means on said stool for supporting an upper of said backup roll assembly when said stool is supported by said lower backup roll assembly. 

1. In a rolling mill having drive side and operating side housings for receiving a pair of work roll assemblies, a window in each of said housings, said work roll assemblies including bearing chock assemblies mounted on their opposite ends and received in said windows, means extending between and connected to the opposite bearing chock assemblies of one of said roll assemblies and including two separate bars arranged on opposite sides of said one roll assembly, support means extending between said housings including two separate support members, ecah having surfaces for supporting a different one of said bars and each having an operative and an inoperative position, means for bringing said support members from their inoperative positions remote from said bars into their operative positions where they assume a supporting relationship with a different one of said bars, and means for engaging one of said roll assemblies for removing said roll assemblies from said mill during which the roll assemblies are supported by said support means.
 2. In a rolling mill according to claim 1 wherein said bars extend between said housing and outside of said windows, each including roll supporting wheels arranged adjacent each of the opposite ends thereof, roll supporting wheels mounted on said bearing chock assemblies of said one roll in a manner that the adjacent wheels of said bars and bearing chock assemblies form cooperating sets, a work roll assembly platform arranged at the operator side of said mill having one of its ends adjacent the outside of said window of said operating housing and adapted to receive and support the wheels of said bearing chock assemblies and bars, and wherein the relative space between the wheels of each cooperating set is such that the respective ends of the roll assemblies are supported at all times by at least one of the wheels of each set as the roll assemblies are removed from the mill and pass through said spaces.
 3. In a rolling mill according to claim 2 in which the axes of said work roll assemblies are arranged in substantially the same vertical plane, and wherein there is means for causing said bearing chock assemblies of the lower work roll assembly to assume a supporting relationship with the bearing chock assemblies of the upper work roll assembly.
 4. In an apparatus for supporting a roll assembly of a rolling mill while the roll assemblies are being removed from and replaced into the mill comprising: said mill including a housing having a window therein that receives said roll assemblies, a side shifting assembly arranged in front of said window, said side shifting assembly comprising three discrete and spaced-apart roll supporting members, one arranged in front of said window in a plane containing the axes of said roll assemblies when mounted in said mill and the other two arranged parallel to and on either side of said first roll supporting member, two movable support means adapted to be selectively supported at any one time by two of said three members, means extending between and interconnecting said support means for causing said support means to move as a unit to and from a position in front of said window, means for effecting said movement of said support means, said support means including means movable with said support means and arranged to bridge said spaces between said members to provide a support for said support means when moving through said spaces, and means for moving a roll assEmbly to and from said window onto one of said support means positioned in front of said window.
 5. In an apparatus according to claim 4 wherein said support means each includes a pair of tracks for supporting a pair of surfaces provided on one of said roll assemblies, rails arranged in said mill alignable with the tracks of said support means when the support means are shifted to a position in front of said window, said means for bridging said spaces comprising liners arranged at the opposite sides of each support means and adjacent said slides having a length greater than said spaces between said member.
 6. In an apparatus according to claim 4 in which said means for effecting movement of said support means includes a power means connected to one of the outside support means.
 7. In an apparatus according to claim 4 including means for stationarily supporting the two outside supporting members, means for movably supporting the central supporting member, and means for effecting said movement of said central supporting member.
 8. In an apparatus according to claim 7 wherein said roll assemblies comprise work roll assemblies and wherein said mill includes a backup roll assembly for each work roll assembly, means in front of said window for supporting said backup roll assemblies when removed from said mill, and said central supporting members including means for engaging one of said backup rolls to effect said removal.
 9. An apparatus according to claim 8 including a stool supportable by one of said support means for transferring to said mill after the work roll assemblies thereof have been removed, means on said stool for allowing it to be supported by a lower of said backup assembly when in said mill, and means on said stool for supporting an upper of said backup roll assembly when said stool is supported by said lower backup roll assembly. 